A “micropores & active species protection” strategy for the preparation of a high-performance Fe/S/N-composited porous carbon catalyst for efficient oxygen reduction reaction and zinc–air batteries

Abstract

Iron porphyrin microporous polymers with hierarchical porous structures and highly uniformly dispersed iron atoms anchored by nitrogen-containing ligands have great potential for the design and preparation of efficient non-noble metal oxygen reduction reaction (ORR) catalysts. Herein, a “micropores & active species protection” strategy is reported to construct a non-noble metal ORR catalyst by introducing polythiophene (PTh) into the porous structure of a tetraphenyl iron porphyrin microporous polymer (FeTPP-MP), followed by carbonization at 900 °C to obtain the Fe/S/N-composited porous carbon catalyst (FeTPP-MP@PTh-900) for the ORR. A comprehensive analysis of the structure and morphology of the resultant FeTPP-MP@PTh-900 reveals that the introduction of PTh not only increases the stability of the porous structure, but also prevents the agglomeration of iron active species during pyrolysis. Meanwhile, PTh as a S source ensures the doping of heteroatom S active sites into the resulting carbon matrix that optimizes the surface electron dispersion of N–S-doped FeTPP-MP@PTh-900 and decreases the work-function of the catalyst. As a result, FeTPP-MP@PTh-900 comprises abundant Fe₂O₃/Fe₃C active species well-dispersed on the N–S-doped carbon matrix, displaying a more positive half-wave potential of 0.89 V than Pt/C (0.84 V) in alkaline electrolyte, and a small Tafel slope of 61 mV dec⁻¹. It also shows outstanding ORR activity and durability in an acidic medium. Finally, FeTPP-MP@PTh-900 can be used as an air cathode for zinc–air batteries, which showed outstanding durability and a superior peak power density of 106 mW cm⁻². The present work offers new prospects for the design of efficient, NPM-based materials for zinc–air batteries.